Britain and Iran have officially restored diplomatic ties, which were severed by London after a group of Iranian hard-liners stormed its Tehran embassy in 2011.

"The U.K. has agreed with Iran that from today [February 20] bilateral relations will be conducted directly through non-resident charge d'affaires and officials," a Foreign Office spokesman was quoted as saying.

Iranian Deputy Foreign Minister Majid Takht-Ravanchi also confirmed to the ISNA news agency that the two countries had re-established direct diplomatic ties.

Relations between the two countries have improved since relative moderate President Hassan Rohani took power in August 2013.